1. Technical Field
The present invention relates to a valve assembly. More particularly, the invention relates to a hemostasis valve assembly for use with a medical device, such as an introducer sheath, to permit substantially leak-free passage therethrough of an interventional device for insertion into a body vessel.
2. Background Information
A variety of well-known medical procedures are performed by introducing an interventional device, such as a catheter, trocar, sheath, stent and the like, into a vessel in a patient's body. Typical procedures for introducing an interventional device into a blood vessel include the well-known Seldinger technique. The Seldinger technique involves opening a blood vessel with a needle, inserting a wire guide into the vessel through the lumen of the needle, withdrawing the needle and inserting a dilator over the wire guide. The dilator is typically located inside an introducer sheath which is also inserted into the vessel, and the dilator is sealed to the sheath by a hemostasis valve through which the dilator passes. The dilator is thereafter removed, and an interventional device is inserted through the sheath and hemostasis valve into the vessel.
As the Seldinger technique and/or other interventional procedures are carried out, care must be taken to avoid the undesirable introduction or leakage of air into the vessel (air embolism), as well as the undesirable leakage of blood, other bodily fluids or cavity-pressurizing gas from the patient. As procedures for introducing catheters and other interventional devices have become more widely accepted, these procedures have become more diverse, and the variety of sizes and types of interventional devices has grown dramatically. As a result, the risk of inward or outward leakage of fluids has increased.
One known way to minimize such leakage is to provide one or more disk-like gaskets (often referred to as check valves) in an elongated passageway of a device through which fluids may pass into or out of the body. Such devices are generally positioned in a housing at a proximal end portion of the introducer, between a main body portion and an end cap. Each disk typically includes one or more slits, apertures, or other configurations extending at least partially through the disk to provide a sealable path to permit insertion of the medical interventional device through the disk, and to substantially prevent the backflow of fluids. Examples of such disks are provided in, among others, U.S. Pat. Nos. 4,430,081, 5,006,113 and 6,416,499, incorporated by reference herein. Such valves are now well known in the medical arts, and additional discussion of their use and function is not necessary for an understanding of the present invention.
Frequently, it is necessary to replace a previously-inserted medical interventional device with another interventional device of a different diameter, or with a different type of device. Such exchanges are often made over a wire guide, wherein the old device is withdrawn over the wire guide, and the new device is thereafter inserted into the body vessel over the existing wire guide or a newly-inserted wire guide. In many such cases, check valves are provided in an attempt to minimize leakage of blood back through the introducer. Such valves are dependent upon the elasticity of the valve body, and its ability to draw back upon itself to seal any gap created upon insertion or withdrawal of a device through the valve.
Known slitted check valves generally include one or more slits that criss-cross and span a center portion of the valve disk, or a hole disposed through the center of the disk. As the interventional device is passed through the center of a slit valve disk, the slits open outwardly and form one or more generally “V”-shaped openings that are disposed along the outer surface of the interventional device. Such linear-type openings often do not form tight seals, and inherently create gaps that permit the leakage of at least some fluid. As a result, these valve systems may comprise two or three such valve sheaths that are aligned in the valve housing in a manner such that the slit portions are not in axial alignment. Although this arrangement may reduce the amount of leakage when compared to the use of a single valve sheath, the presence of the gaps provides a conduit from which some leakage may occur. Similarly, the various flaps resulting from the slits do not always re-set in the proper manner following passage of the interventional device, thereby creating additional gaps through which fluid may leak.
Small size interventional devices are often delicate, and possess little hoop strength. When such devices pass through a check valve sheath, the thickness and strength of the valve sheath may cause damage to the delicate structure of the interventional device. In this case, the clearance between the opening in the disk and the interventional device can be so slight that it may be difficult to insert and/or withdraw the interventional device. In addition, on some occasions, additional small diameter tubing must be used to keep the valve open so that a catheter or other device may be passed therethrough. When additional equipment is required, such as a small diameter tube or a Tuohy-Borst valve, the surgeon's hands, and attention, may be unduly distracted at the very time when primary focus is most preferably directed to the task at hand.
When one or more valve disks having a hole through the center of the disk are used, the disks will only recover back to the size of the center hole following removal of the catheter. As a result, the respective center holes allow leakage once the catheter is removed. Such valves may be satisfactory when there is no need to remove the catheter that seals the opening; however, they can be problematic when the catheter is removed and the center opening is left unoccluded.
It is desired to provide a hemostasis valve assembly for a medical device that provides an effective seal, and that avoids the problems encountered with prior art seals.